Hi, my Goodman Gas Furnace fan is running but no flames. This isn't the first time I've had this problem. This happened once before in March of 2011 but thanks to hvactechfw and seattlepete I got it working. It's been working fine since then but now I have the same problem but the fixes I got before aren't working. I'll break it down, but here's the old thread:

http://www.doityourself.com/forum/ga...ng-lights.html

Thermostat works fine, calls for power and fan runs, but no heat.

Red service light flashes 3 times. According to manual: "Pressure switch failure to close" suggesting I check "Pressure switch stuck closed".

Using a paperclip, I bypassed the pressure switch but it will still not fire. (I have replaced pressure switch in the past)

I disconnected galvanized exhaust pipe let it run for a few minutes. No fire. Air flow seems strong and unobstructed.

As proposed by SeattlePete the last time this happened I tried this fix:
"Remove the hose from the inducer motor housing. Use a small diameter drill bit to run into the nipple and clean out any corrosion. You need to be sure to have a small drill bit and to get into the middle of the nipple so that it gets into the inducer motor housing."

This is actually what fixed my problem last time around. Several times I have used a 1/15" drill bit to lightly ream out the nipple, but this time no luck. However, I'm not even getting it to fire when I bypass the switch. Because I can't even get it running with the switch bypassed, does this mean the nipple corrosion is certainly NOT the problem?

Furnace model: GMP075-3 Rev B
manual:
http://www.hvacpartsshop.com/Gmph075-4%20Series.Pdf

Actual pics of model label as well as some other shots:
Furnacedesc.jpg picture by mypicstrix - Photobucket

After sitting since last winter furnace was running for a little bit this season before breaking down. We've had a few cold days so it's been on and off.

I've had a "true steam" humidifier running for a few years now. It's mounted vertically on the outtake vent. When I was changing the tank last month, more than a few drips may have rained down on the furnace through the top vent. (Drips happened OUTSIDE duct, down onto top of furnace cover). Since that time furnace had been running fine and there doesn't seem to be any electrical problem. Just thought I'd better mention everything.

hvactechfw suggested my furnace model has been known to have problems with cracked heat exchangers (see old thread). Although I'm very good about keeping the batteries in my carbonmonoxide detector, I have to admit, I never did get around to checking the heat exchanger for cracks. This wasn't related to problem last time, but again, just wanted to mention everything.

Temps are just above freezing here right now but I've got a wood stove and a ceramic heater keeping up.

I haven't given up trying to fix this problem and I haven't called in the pros yet, but I am considering if I'll need to buy a new furnace. Last time hvactechfw helped me determine this model was build in 1998. I bought the home in 2000, so I assume it was installed and running not long after 1998. I believe it was also hvactechfw who told me gas furnaces last 15-20 years (national average). That would put me no older than 14 years, but I'm wondering at what point I consider buying a new one, especially considering possible problem with the heat exchangers. Not sure if they've made any big strides in efficiency or if rebates are available, etc.

ANY help is appreciated the sooner the better. We have no heat, and naturally it's the weekend.

 

Back AGAIN???


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The pressure switch is a key safety component, so the control module is checking not only to see if the pressure switch is closing, but also whether it opens when the inducer motor is off.

Obviously, if it's stuck closed it is not working properly and could allow an unsafe condition to occur.

So it appears that the control module is finding that the pressure switch is failing to open as it should. You might test that with a multimeter to see if that is actually happening.

Obviously, if it's stuck closed, jumpering the pressure switch is not going to solve that problem.

 

SeattlePioneer,

Yep, back again. Sorry I fudged your name in my OP. First, thanks for getting back to me so soon. Had internet problems all morning so late answering you.

I'm familiar with electrical safety and have done a lot of my own work at home running romex and I follow code well. However, although I have a MM, I'm not well versed in it's use and I'm a little confused on how to test if the switch is opened. Two wires run into the switch attached with clips. For my first test, I just disconnected them from the switch then joined them with a paperclip to test. I understand what you mean by checking for open and why that would prevent operation, but I'm confused as to HOW to check for open. Do I need access to the circuit board of the control module or can I do this using the two wires via some setting on the MM? If so, when using the MM, am I setting it to AC 250 or just 125 or is this just some kind of continuity test setting? Where do I set the MM? Please dumb it down for me. You won't insult my intelligence.

If I am checking the circuit board, you might find part of the image here just to get me in the right place....(these are my photos of the furnace)
Furnacedesc.jpg picture by mypicstrix - Photobucket

I'm actually pretty handy and willing to safely do the work, so please don't take my ignorance here for incapability. Even if I hire a pro to do the work, I like to do as much of the troubleshooting myself. Past experience with you guys here has shown me the locals aren't usually as well informed as the regulars here.

Thanks for your help and patience.

 

The pressure switch is typically a small pancake shaped piece of polished metal with two wire connections to it. It would have one or more rubber hoses going from the pressure switch into a connection in the burner compartment.

Set your multimeter to be able to measure 24 VAC or less ---- it might have a setting for 50 VAC, or 100 VAC. Use the next largest setting to 24 VAC.

Connect one clip to the furnace sheet metal chassis, which is ground.

With the thermostat calling for heat and the inducer motor running, measure the voltage on both electrical connections to the pressure switch. If 24 VAC appears on only one side of the pressure switch, the switch is open. If 24 VAC appears on both electruical connections on the pressure switch, the switch is closed.

 

Again, thanks for the help.

Okay, first I need to clear up some foolishness on my part. The paperclip test I did wasn't me bypassing the pressure switch. It was me bypassing the LIMIT switch. I somehow mixed these two up because of a problem I had a while back with the LIMIT switch. I did replace the limit switch years ago, but I have never replaced the pressure switch. I actually had a pressure switch on order and was going to replace it when I finally performed your corrosion clean-out trick and that saved me from having to do anything else. I never installed the new pressure switch, just sent it back. I actually don't remember ever bypassing the pressure switch before.

So right NOW, using the paperclip again, I joined the two wires on the PRESSURE switch just now. When I do that and THEN turn on power, I get nothing. The fan won't even start up even though I know the thermostat is calling for heat. I remove the paperclip and put the wires back to the pressure switch, turn power on, and I get fan immediately, but of course no heat. With wires totally disconnected from the pressure switch, when I turn the power on, I get the fan, but no heat.

Okay, on to the multimeter test. My MM lists ACV, not VAC, but assuming both mean alternating current voltage, I went with that. 500/250/10 are my only choices, so I set to 250. I've got both wires disconnected from the pressure switch for testing. Furnace power on, fan is running and it's calling for heat. I measure one of the wire leads and get a reading. I measure the second one and get no reading. I performed the same test with the pressure switch reconnected to the wires, and got the same result. Therefore, if I understand you, the the switch is open, and NOT stuck closed. So I guess that means the pressure switch is okay? What next?

 

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This test indicates that the pressure switch isn't closing.

When the inducer motor comes up to speed, the pressure switch ought to close.


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Try having the power to the furnace on with the inducer motor running and then connecting the two pressure switch connections (which bypasses the pressure switch).

 

Okay, wires disconnected from pressure switch. Power on. Fan comes on and I wait about 20 secs. Then I join the two wires. About 10 seconds later, FIRE ON! All three burners are go. I pull connection apart and instantly heat goes off.

So, does this mean I need a new pressure switch? Problem solved?

 

Not so simple.

What you have verified is that the pressure switch isn't closing. It is there to insure that there is a proper flow of combustion air through the furnace. If there isn't, a variety of Bad Things can happen.

Unfortunately, a wide variety of things can cause the pressure switch not to close.

Start by disconnecting the vent pipe. Check for any obstructions to the vent pipe or chimney, and see if the furnace will fire up when the vent pipe is disconnected.

Also check that the robber hose to the pressure switch isn't cracked or obstructed with water, corrosion or debris.

 

I've only been using the furnace for testing since this started, then I turn it off. The 4" galvanized vent pipe has been disconnected the whole time so it's just venting into the basement and has strong air flow from the fan. I've removed the black hose and inspected it. Good flexibility when I blow through it, it seems totally clear. I cut off a half inch from each end of the hose to assure a fresh snug fit on the nipples, not that it seemed like it needed it. Even did the drill bit twist for corrosion one more time.

No luck.

Edit: Furnace filter is clean and has been changed regularly.

 

Sometimes corrosion can block the air sampling port for the pressure switch where it connects to the furnace.

Disconnect the rubber hose where it connects to the furnace. Use a small diameter drill bit to clean out any obstructions inside that fitting. The drill bit probably needs to be smaller than you would think to be able to get into the port to do the cleaning job properly.

The drill bit is going to enter the area occupied by the fan blades, which aren't especially susceptible to damage.

 

Yeah, that's the FIRST thing I did. Remember, this is how we solved the problem last time back in the old post. I used about a 1/16" inch bit and it went considerably deeper than a thicker bit would have. I've actually done this several times including just before the last post.

 

Yes, you posted that in your first post.


You can take out the inducer motor and inspect the fan for being plugged with debris or broken blades.

That exposes the top of the heat exchanger as well, and you can look for evidence of black soot or other debris that might be plugging up the works.

 

Well, I haven't actually removed the inducer motor yet. I removed four screws at 12, 3, 6, and 9 o'clock but it wasn't pulling off easy. I believe I removed this before and had to replace the gasket with a liquid one which is now acting like a glue. I'm sure I could get it off if I had to, but I wanted to make sure I wasn't making this harder than necessary. Referring to this picture below. You'll see the front black hub which spins with the fan. This is part of a grey body of metal that's fastened to the WHISTLE shaped housing. This grey metal looks like pot metal and although it looks fastened in three places, it looks like looking at the nut or thread end and there's no way to loosen from this side. When I said I removed the four screws I meant from the "whistle" shaped assembly. However, there's also an option to remove the panel that the whistle shaped panel is attached to which has many screws, much larger and has a square shape. This one also appears to have a gasket which I may or may not have removed before. Don't remember.

With the galvanized vent removed I was able to give it a good cleaning with the shop vac. I tried to get deep down in there and even used a larger hose to suck from the nipple that takes the rubber hose. But this didn't make any difference.

I'm still willing to remove the motor and clean better, but wasn't sure what the easiest way would be to do this. Doesn't seem to be a way to remove the grey metal body, but I could remove the "Whistle" or the larger square back. Not sure if the gasket will survive removal which means I'll need to run out and get some more material to replace everything. Or, if you have something else to try maybe I could do that and come back to this?

Thanks. I know we've been at this all day. Let me know if you're done checking in for the night. Needless to say I really appreciate your time.

Please check this photo. It will make more sense of what I'm saying.

full.jpg picture by mypicstrix - Photobucket

Edit: This looks like my part.
http://www.myhvacparts.com/store/med...ts/goodma5.jpg

 

My recollection is that you pull off the motor and a piece of sheet metal which is bolted onto the larger fan housing assembly.

The motor goes through the sheet metal and the fan threads on to the motor, so the motor, sheet metal piece and fan come off together.

I could only open the second of your two pictures.

 

Well, son f a something

It was that nipple again. LOL. I can't believe. AFTER I got the inductor off I was able to really get a handle on it. I guess I just didn't go deep enough with the drill bit but if felt like I did. Sheesh. Just can't believe this got me twice. lol.

So, the gasket holding the inductor to the main body was a liquid one I put on a couple years ago. Even so, now that it's back in place it looks like its sealing well. Can I run it tonight or should I wait and pickup some liquid gasket tomorrow? BTW, if I do that, what heat rating does it need to be?

Thanks (again) for all your help.

 

Go ahead and run it. If the sealing wasn't adequate, the pressure switch wouldn't close.

There a crook above the inducer motor housing that is a good place to leave a drill bit of a suitable size. Having the right drill bit handy makes it easy to clean out the fitting.

 

Cool. So I don't need to change the gasket any time soon? That's good. I guess if I get the same 3 blinks I'll know to check the gasket.

Thanks again for all your help. Really.

I think I may need to embellish this story a bit when I tell the wife.

Have a good one.

 

petethebuilder,
I am hoping you still look at this thread and might have a suggestion...

When the thermostat is on auto, the blower kicks on for a few minutes blowing cold air, and then stops. When the thermostat is turned to 'on', the blower continuously blows cold air, until turned off.

I thought it was the ignitor, and that it turning off after a few minutes was the safety turning the unit off after a couple tries. But the light was blinking 3 times as well. Our unit is approximately 13 years old and located outside.

HVAC tech came out today, and as he was removing the service panel said 'your inducer is shot'... and I was curious how he knew this immediately.

I asked him their price to replace it and he responded $1000. He tested several wires, but I'm not exactly sure which ones or what he found out.

As he was doing this, I googled the model number of the inducer, and found them available at many stores for ~$150. I told him this, and he got a bit defensive and said, 'well of course our company has to mark things up somewhat, and ours includes a one year warranty' (as do the parts I found online). He then said we would be better off replacing the unit, which he could do for $6500... since it was 13 years old.

He never took the inducer off, looked for any obstructions, etc.

So I figured that if we need to replace the unit, I might as well try trouble shooting a bit myself. I was planning on using some of the tips from this thread, and was wondering exactly which tube it is that helped you fix the problem twice.

I saw some of your pictures, but others wouldn't load... so I couldn't see if there was a picture of the inducer and the tube you mentioned drilling out to clean.

I am much less knowledgeable in HVAC issues compared to you, but I am capable with instructions! Is the Inducer something that I can safetly repair/replace? What are my risks...breaking something and really needing a professional to come out (which is where I am at now)? Is there a risk that I can do something that would allow carbon monoxide in the house, or is there a safety that would detect that?

Any other advice would be greatly appreciated...

Geo

 

It's confusing, and can therefore be bad, to revive an old thread.

I'd suggest you copy your post and paste it into a new thread and we'll see if we can be of help.

 

I know that this thread is old but I have been reading for hours over the last 2 days trying to figure out what is wrong with my furnace that is giving the pressure sensor error code. I was just about to give up when I stumbled on this thread and decided to read it while taking a break from the furnace. In all that I have read this is the first time that anyone one had brought up blockage on the fan side of the hose. After reading I connected the hose to the fan nipple and blew into it. I immediately noticed that it was clogged. I inserted a piece of wire that was laying near by and was able to clear it out. I then tested my furnace and it worked perfectly! Thank you guys. You saved me some cash and another cold night for my family.

 

"Remove the hose from the inducer motor housing. Use a small diameter drill bit to run into the nipple and clean out any corrosion. You need to be sure to have a small drill bit and to get into the middle of the nipple so that it gets into the inducer motor housing."

I would just like to thank all in this thread for helping me fix my own similar problem with the above mentioned piece of advice. It saved me a lot of money and a cold night.

 

Just paid a repair guy$120 to fix the exact same issue. The valve wasn't bad-there was a spider web in the gas line. Small spiders find the smell of gas irresistible and build webs in the valves and so the gas doesn't get through. I was so excited I didn't have to pay to replace the entire valve. Spiders, I had no idea...

 

Welcome to the forums.

We leave old threads online to be used for reference.

Glad you got your problem fixed but:

This thread you posted in is discussing problems with the draft inducer blower.
Your problem was a clog in the burner. Not a related problem.

 

THANK YOU!!!
I had a problem today with my Goodman, and thanks SeattlePioneer, I pulled the little rubber hose off the blower, cleared it with a paperclip, and it fired up again!

DOITYOURSELF.COM THANK YOU THANK YOU EVERYTIME!!!

 

Obviously this has been a very helpful thread. It will always remain available in our searchable archives. If after reading this thread you still have a problem or questions..... please feel free to start a new thread.